The Distribution Box

The distribution box lies between the septic tank and the drainfield, and serves to evenly distribute the wastewater evenly amongst the drainfield lines. Ensuring even distribution of the wastewater is crucial in maintaining the longevity of the drainfield. If only a small portion of the drainfield is actually used due to poor distribution, localized saturation of a drainfield line may occur. Organic matter and solids may build up faster than they are broken down by soil microbes clogging soil pores, causing the drainfield to fail prematurely. A typical D-box is pre-cast with multiple holes, as seen here, to allow for use in various system configurations. For example, the drainfield lines may be located in various positions relative to the incoming pipe; on either side of the D-box, both on one side, etc. The D-box shown here has three pipes; one delivering wastewater from the primary treatment tank, and two to distribute effluent to the two drainfield lines or trenches.